Method and device for high-capacity entrained flow gasifier

ABSTRACT

A method and device for the gasification of pulverized fuels from solid fuels such as bituminous coals, lignite coals, and their cokes, petroleum cokes, coke from peat or biomass, in entrained flow, with an oxidizing medium containing free oxygen, by partial oxidation at pressures between atmospheric pressure and 80 bar, and at temperatures between 1,200 and 1,900° C., at high reactor capacities between 1,000 and 1,500 MW. The method uses the following steps: metering of the fuel, gasification reaction in a gasification reactor with cooled reaction chamber contour, quench-cooling, crude gas scrubbing, and partial condensation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for entrained flow gasification withvery high capacity that can be used for supplying large-scale syntheseswith synthesis gas. The invention enables the conversion of fuelsrefined into pulverized fuel, such as lignite and bituminous coals,petroleum coke, solid grindable refuse, and solid-liquid suspensions,so-called slurries, into synthesis gas. The fuel is reacted attemperatures between 1,200 and 1,900° C. with a gasification mediumcontaining free oxygen, at pressures up to 80 bar, by partial oxidationto gases containing CO and H₂. This is done in a gasification reactorthat is distinguished by a multiple-burner system and by a cooledgasification chamber.

2. The Prior Art

The autothermic entrained flow gasification of solid, liquid, andgaseous fuels has been known in the technology of gas production foryears. The ratio of fuel to gasification medium containing oxygen ischosen so that higher carbon compounds are completely cracked forreasons of synthesis gas quality into synthesis gas components such asCO and H₂, and the inorganic components are discharged as molten slag;see J. Carl, P. Fritz, NOELL-KONVERSIONSVERFAHREN, EF-Verlag fürEnergie- und Umwelttechnik GmbH, 1996, p. 33 and p. 73.

According to various systems used in industry, gasification gas andmolten slag can be discharged separately or together from the reactionchamber of the gasification device, as shown in German Patent No. DE 197131 A1. Either systems with refractory linings or cooled systems areused for the internal confinement of the reaction chamber structure ofthe gasification system; see German Patent No. DE 4446 803 A1.

European Patent No. EP 0677 567 B1 and International Publication No. WO96/17904 show a method in which the gasification chamber is confined bya refractory lining. This has the drawback that the refractory masonryis loosened by the liquid slag formed during gasification, which leadsto rapid wear and high repair costs. This wear process increases withincreasing ash content. Thus, such gasification systems have a limitedservice life before replacing the lining. Also, the gasificationtemperature and the ash content of the fuel are limited; see C. Higmanand M. van der Burgt, “Gasification”, Verlag ELSEVIER, USA, 2003. Aquenching or cooling system is also described, with which the hotgasification gas and the liquid slag are carried off together through aconduit that begins at the bottom of the reaction chamber, and are fedinto a water bath. This joint discharge of gasification gas and slag canlead to plugging of the conduit and thus to limitation of availability.

German Patent No. DE 3534015 A1 shows a method in which the gasificationmedia, powdered fuel and oxidizing medium containing oxygen, areintroduced into the reaction chamber symmetrically through multipleburners in such a way that the flames are mutually diverted. Thegasification gas loaded with powdered dust flows upward and the slagflows downward into a slag-cooling system. As a rule, there is a deviceabove the gasification chamber for indirect cooling utilizing the wasteheat. However, because of entrained liquid slag particles, there is thedanger of deposition and coating of heat exchanger surfaces, whichhinders heat transfer and may lead to plugging of the pipe system and/orerosion. The danger of plugging is counteracted by taking away the hotcrude gas with a circulated cooling gas.

Ch. Higmann and M. van der Burgt in “Gasification”, page 124, VerlagElsevier 2003, describe a method in which the hot gasification gasleaves the gasifier together with the liquid slag and directly enters awaste heat boiler positioned perpendicularly below it, in which thecrude gas and the slag are cooled with utilization of the waste heat toproduce steam. The slag is collected in a water bath, while the cooledcrude gas leaves the waste heat boiler from the side. A series ofdrawbacks detract from the advantage of waste heat recovery by thissystem. Deposits form on the heat exchanger tubes, which lead tohindrance of heat transfer and to corrosion and erosion, and thus tolack of availability.

Chinese Patent No. CN 200 4200 200 7.1 describes a “Solid PulverizedFuel Gasifier”, in which the powdered coal is fed in pneumatically andgasification gas and liquefied slag are introduced into a water baththrough a central pipe for further cooling. This central discharge inthe central pipe is susceptible to plugging that interferes with theoverall operation, and reduces the availability of the entire system.

The capacity of the various gasification technologies mentioned islimited to about 500 MW, which is attributable in particular to the fuelinfeed to the gasification reactor.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a gasificationmethod that permits maximum capacities of 1,000 to 1,500 MW withreliable and safe operation.

This object is achieved by a gasification method for the gasification ofsolid fuels containing ash at very high capacities with an oxidizingmedium containing oxygen based on an entrained flow reactor whosereaction chamber contour is confined by a cooling system, with thepressure in the cooling system always being kept higher than thepressure in the reaction chamber. The process for preparing the fuel andfeeding it to the gasification burners is as follows: with dry pneumaticinfeed by the dense-flow transport principle, the fuel is dried,pulverized to a grain size of <200 μm, and passed through operationalbunkers to pressurized sluices, in which the dust-like fuel is broughtto the desired gasification pressure by introducing a non-condensing gassuch as N₂ or CO₂. Different fuels can be used here at the same time.Via a system of multiple such pressurized sluices, they can be loadedand pressurized alternately. The dust under pressure then is sent tometering tanks, in the bottom of which a very dense fluidized bed isproduced by likewise introducing a non-condensing gas, with one or moretransport pipes immersed in the bed and opening into the burners of thegasification reactor. A separate infeed and metering system isassociated with each high-capacity burner. The fluidized fuel dust flowsto the burners by applying a pressure differential between the meteringtanks and the burners of the gasification reactor. The amount of flowingfuel dust is measured, regulated, and monitored by measurement devicesand monitors.

With the reactor according to the invention, there is still also theability to pulverize the undried fuel to a grain size of <200 μm and tomix the pulverized fuel with water or oil and to feed it as a slurry tothe burners of the gasification reactor. The method of infeed, which isnot described at this point, is configured by one skilled in the artaccording to known methods.

An oxidizing medium containing free oxygen is supplied to the burners atthe same time, and the slurry is converted to crude synthesis gas bypartial oxidation. The gasification takes place at temperatures between1,200 and 1,900° C. and at pressures up to 80 bar. The reactor has acooled reaction chamber contour that is made up of a cooling shield.This consists of a tubular shield welded gas-tight that is studded andlined with a material that is a good heat conductor.

The crude gas produced in the gasification reactor leaves thegasification reactor together with the liquid slag formed from the fuelash and is sent to a chamber located perpendicularly below it, in whichthe hot crude gas and the liquid slag are cooled by injecting water. Thegas can be cooled completely down to the condensation point of the gasby spraying in excess water. The temperature is then between 180 and240° C., depending on the pressure. However, it is also possible to feedin only a limited amount of cooling water and to cool the crude gas andslag by partial cooling to 700 to 1,100° C., for example, and then toutilize the sensible heat of the crude gas to produce steam in a wasteheat boiler. Partial quenching or partial cooling prevents or sharplyreduces the risk of slag caking on the tubes of the waste heat boiler.The water or recycled gas condensate needed for complete or partialcooling is supplied through nozzles that are located directly on thejacket of the cooling chamber. The cooled slag is collected in a waterbath and is discharged from the process. The crude gas cooled totemperatures between 200 and 300° C. is then sent to a crude gasscrubber, which is preferably a Venturi scrubber.

The entrained dust is thereby removed down to a particle size of about20 μm. This degree of purity is still inadequate for carrying outsubsequent catalytic processes, for example crude gas conversion. Saltmists are also entrained in the crude gas, which have detached from thepowdered fuel during gasification and are carried off with the crudegas. To remove both the fine dust <20 μm and the salt mists, thescrubbed crude gas is fed to a condensation step in which the crude gasis chilled indirectly by 5 to 10° C. Water is thereby condensed from thecrude gas saturated with steam, which takes up the described fine dustand salt particles. The condensed water containing the dust and saltparticles is separated from the crude gas in a following separator. Thecrude gas purified in this way can then be fed directly, for example, toa desulfurization system.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the present invention will become apparentfrom the following detailed description considered in connection withthe accompanying drawings. It is to be understood, however, that thedrawings are designed as an illustration only and not as a definition ofthe limits of the invention.

In the drawings, wherein similar reference characters denote similarelements throughout the several views:

FIG. 1 shows a block diagram of the technology according to theinvention;

FIG. 2 shows a metering system for pulverized fuel according to theinvention;

FIG. 3 shows a device for feeding pulverized fuel for high-capacitygenerators;

FIG. 4 shows a gasification reactor with full quenching; and

FIG. 5 shows a gasification reactor with partial quenching.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a block diagram of the process steps of pneumatic meteringof pulverized fuel, gasification in a gasification reactor with cooledreaction chamber structure 2, quench-cooling 3, crude gas scrubbing 4,in which there can be a waste heat boiler 4.1 between the quench-cooling3 and the crude gas scrubbing 4, and a condensation or partialcondensation 5 follows the crude gas scrubber 4.

FIG. 2 shows a metering system for pulverized fuel consisting of abunker 1.1 followed by two pressurized sluices 1.2, into which leadlines 1.6 for inert gas, and at the top of which depressurization lines1.7 exit, with lines to the metering tank 1.3 leaving the pressurizedsluices 1.2 from the bottom. There are fittings on the pressurizedsluices 1.2 for monitoring and regulating. A line 1.5 for fluidizing gasleads into the metering tank from below, which provides for fluidizingthe gas, and the fluidized pulverized fuel is fed through the transportline 1.4 to a gasification reactor 2.

FIG. 3 shows another design of the device for feeding pulverized fuelfor high-capacity generators 2, wherein a bunker 1.1 has threedischarges for pulverized fuel, each leading to pressurized sluices 1.2,with each of the three pressurized sluices transporting pulverized fuelstreams to one of three metering tanks 1.3, from which transport lines1.3 lead to the dust burners 1.2 with oxygen infeed of the reactor.There are three dust burners 2.1 on each reactor 2 with oxygen feed,with an ignition and pilot burner 2.2 to start the reaction. Because ofsuch intensive fluidized fuel flows and the presence of three burners2.1, it is possible to achieve maximum capacities of 1,000 to 1,500megawatts with reliable and safe operation.

FIG. 4 shows a gasification reactor 2 with full quenching 3, with theignition and pilot burner 2.2 and the dust burners 2.1, through whichthe fluidizing gas or a slurry of fuel and liquid is fed into thereactor, being positioned in the center of the head of the reactor 2.The reactor has a gasification chamber 2.3 with a cooling shield 2.4whose outlet opening 2.5 leads to the quench-cooler 3, whose quenchingchamber 3.1 has quenching nozzles 3.2, 3.3, and a crude gas discharge3.4, through which the finished crude gas can leave the quench-cooler 3.The slag that leaves the quench-cooler through an outlet opening 3.6 iscooled in the water bath 3.5.

FIG. 5 shows a gasification reactor 2 with partial quenching, with thegasification reactor located in the upper part, in which dust burners2.1 gasify the dust from the transport line 1.4, and with an ignitionand pilot burner 2.2 positioned in the center. Gasification reactor 2has a bottom opening into quenching chamber 3.1, into both sides ofwhich lead quenching nozzles 3.2, with waste heat boilers 4.1 placedbelow this.

The function will be described with a first example with reference tomaterial flows and procedural processes:

240 Mg/h of pulverized coal is fed to a gasification reactor with agross capacity of 1500 MW. This pulverized fuel prepared by drying andgrinding crude bituminous coal has a moisture content of 5.8%, an ashcontent of 13 wt. %, and a calorific value of 24,700 kJ/kg. Thegasification takes place at 1,550° C., and the amount of oxygen neededis 208,000 m³ I. H./h. The crude coal is first fed to a state-of-the-artdrying and grinding system in which the water content is reduced to 1.8wt. %. The grain size range of the pulverized fuel produced from thecrude coal is between 0 and 200 μm. The ground pulverized fuel (FIG. 1)is then fed to the metering system, the functional principle of which isshown in FIG. 2. The metering system consists of three identical units,as shown in FIG. 3, with each unit supplying ⅓ of the total amount ofpowder, or 80 Mg/h, each to a dust burner. The three dust burnersassigned to them are at the head of the gasification reactor, whoseprinciple is shown in FIG. 4. The usable pulverized fuel according toFIG. 2, which shows one unit of the powder metering system, goes fromthe operational bunker 1.1 to alternately operated pressurized sluices1.2. There are 3 pressurized sluices in each unit. Pressurizedsuspension to the gasification pressure is performed with an inert gassuch as nitrogen, for example, which is fed in through the line 1.6.After suspension, the pressurized pulverized fuel is fed to the meteringtank 1.3. The pressurized sluices 1.2 are depressurized through the line1.7 and can be refilled with pulverized fuel. The 3 mentionedpressurized sluices in each unit are loaded alternately, emptied intothe metering tank, and depressurized. This process then begins anew. Adense fluidized bed is produced in the bottom of the metering tank 1.3by feeding in a dry inert gas through the line 1.5, likewise nitrogen,for example, that serves as the transport gas; 3 dust-transport lines1.4 are immersed in the fluidized bed. The amount of pulverized fuelflowing in the transport lines 1.4 is measured and regulated in relationto the gasification oxygen. The transport density is 250-420 kg/m³.

The gasification reactor 2 is shown and further explained in FIG. 3. Thepulverized fuel flowing through the transport lines 1.4 to thegasification reactor 2 is discharged into 3 metering systems, each witha capacity of 80 Mg/h. The total of 9 transport lines 1.4 lead in groupsof three each to 3 gasification burners 4.1 located at the head ofreactor 2. At the same time, ⅓ of the total amount of oxygen of 208,000m³NTP/h is fed to each gasification burner. The dust burners arearranged symmetrically at angles of 120°, and in the center there is anignition and pilot burner that heats the gasification reactor 2 andserves to ignite the dust burner 4.1. The gasification reaction, or thepartial oxidation at temperatures of 1,550° C., takes place in thegasification chamber 2.3, which is distinguished by a cooled reactionchamber contour 2.4. The monitored and measured amount of pulverizedfuel is subjected to ratio regulation with the supplied oxygen, whichprovides that the ratio of oxygen to fuel neither exceeds nor fallsbelow a range of λ=0.35 to 0.65. The value of λ represents the ratio ofthe needed amount of oxygen for the desired partial oxidation to theamount of oxygen that would be necessary for complete combustion of thefuel used. The amount of crude gas formed is 463,000 m³NTP/h and isdistinguished by the following analysis: H₂ 19.8 vol. % CO 70.3 vol. %CO₂ 5.8 vol. % N₂ 3.8 vol. % NH₃ 0.03 vol. % HCN 0.003 vol. % COS 0.04vol. % H₂S 0.4 vol. %

The hot crude gas at 1,550° C. leaves the gasification chamber 2.3together with the liquid slag through the discharge 2.5 and is cooled to212° C. in the quenching chamber 3.1 by injecting water through the rowsof nozzles 3.2 and 3.3, and is then sent through the outlet 3.4 to thecrude gas scrubber 4, which serves as a water scrubber to remove dust.The cooled slag is collected in a water bath 3.5 and is dischargeddownward. The crude gas washed with water after the water scrubber 4 issent for partial condensation 5 to remove fine dust <20 μm in size andsalt mists not separated in the water scrubber 4. For this purpose, thecrude gas is cooled by about 5° C., with the salt particles dissolvingin the condensed water droplets. The purified crude gas saturated withsteam can then be fed directly to a catalytic crude gas converter or toother treatment stages.

According to Example 2, the process of pulverized fuel feed is to occuraccording to FIG. 2 and FIG. 3, and the actual gasification in the sameway as in Example 1. The hot crude gas and the hot liquid slag likewisepass through discharge 2.5 into a quenching chamber 3.1, in which thecrude gas is cooled to temperatures of 700-1,100° C., not with excesswater, but only by spraying in a limited amount of water through nozzlerings 3.2, and are then sent to the waste heat boiler 4.1 to utilize theheat of the crude gas to produce steam (FIG. 5). The temperature of thepartially cooled crude gas is chosen so that the slag particlesentrained by it are cooled in such a way as to prevent deposition on theheat exchanger tubes. As in Example 1, the crude gas cooled to about200° C. is then fed to the water scrubber and partial condensation.

Accordingly, while only a few embodiments of the present invention havebeen shown and described, it is obvious that many changes andmodifications may be made thereunto without departing from the spiritand scope of the invention.

LIST OF REFERENCE SYMBOLS USED

1. Pneumatic metering systems for pulverized fuel

1.1 Bunker

1.2 Pressurized sluice

1.3 Metering tank

1.4 Transport line

1.5 Line for fluidizing gas.

1.6 Line for inert gas into 1.2

1.7 Depressurization line from 1.2

2. Gasification reactor with cooled reaction chamber structure

2.1 Dust burner with oxygen infeed

2.2 Ignition and pilot burner

2.3 Gasification chamber

2.4 Cooling shield

2.5 Discharge opening

3 Quenching cooler

3.1 Quenching chamber

3.2 Quenching nozzles

3.3 Quenching nozzles

3.4 Crude gas outlet

3.5 Water bath with slag

3.6 Bottom discharge from 3

3.7 Lining

4 Crude gas scrubber

4.1 Waste heat boiler

5 Condensation, partial condensation

1. A method for the gasification of pulverized fuels from solid fuels such as bituminous coals, lignite coals, and their cokes, petroleum cokes, coke from peat or biomass, in entrained flow, with an oxidizing medium containing free oxygen, comprising the following steps; supplying a fuel with a water content <10 wt. % and a grain size <200 μm to multiple identically engaged metering systems that feed the fuel through transport pipes to multiple gasification burners located at a head of a reactor, said burners being symmetrically arranged and containing additional oxygen infeeds; igniting said multiple burners with oxygen infeed in the head of the reactor by ignition and pilot burners; determining quantities of the fuel and oxygen fed to the burners, and determining an overall total of all amounts of fuel and oxygen supplied to the burners, regulating an oxygen ratio with a regulating mechanism that ensures that the oxygen ratio neither exceeds nor falls below a ratio of 0.35 to 0.65, regardless of the distribution of fuel and oxygen to the burners; converting the fuel in the gasification reactor at temperatures between 1,200 and 1,900° C. and at pressures between atmospheric pressure and 80 bar, into a crude synthesis gas and slag; cooling the crude gas at 1,200 to 1,900° C. and the slag down to a condensation point at temperatures between 180° C. and 240° C. in a quenching cooler by injecting water; and feeding the cooled crude gas to further treatment stages.
 2. A method pursuant to claim 1, wherein there are three metering systems conducting fuel streams through transport pipes to three burners.
 3. A method pursuant to claim 1, wherein the fuel has a grain size of <100 μm.
 4. A method pursuant to claim 1, wherein the fuel has a water content of <2 wt. %.
 5. A method pursuant to claim 1, wherein the fuel is fed to the reactor in as a pulverized fuel-in-water slurry, with each burner having its own infeed system.
 6. A method pursuant to claim 1, wherein the fuel is fed to the reactor as a pulverized fuel-in-oil slurry, with each burner having its own infeed system.
 7. A method pursuant to claim 1, wherein more than one fuel is gasified at the same time.
 8. A method pursuant to claim 1, wherein a different fuel is gasified by each burner.
 9. A method pursuant to claim 1, wherein the fuel is fed through the burners pneumatically or as a slurry.
 10. A method pursuant to claim 1, further comprising the steps of partial cooling to temperatures between 700 and 1,100° C. and waste heat recovery by steam generation from the heat of the crude gas, following the step of converting.
 11. A device for the gasification of pulverized fuels from solid fuels such as bituminous coals, lignite coals, and their cokes, petroleum cokes, coke from peat or biomass, in entrained flow, with an oxidizing medium containing free oxygen, comprising: a metering system for passing multiple streams of pulverized fuel, comprising a bunker connected to pressurized sluices that conduct the streams of pulverized fuel to metering tanks, and multiple transport lines running from the metering tanks; a high-capacity reactor connected to the transport lines, said reactor having multiple gasification burners and an ignition and pilot burner symmetrically arranged at a head of the reactor; a measuring system at the gasification burners to measure and regulate amounts of pulverized fuel and oxygen flowing in, with integral monitoring and regulation of overall total amounts of pulverized fuel and oxygen flowing to the reactor; a quenching chamber connected to the reactor to cool crude gas and slag produced in the reactor; a crude gas scrubber connected to the quenching chamber; a cooler connected to the scrubber for performing a partial condensation.
 12. A device for the gasification of pulverized fuels from solid fuels such as bituminous coals, lignite coals, and their cokes, petroleum cokes, coke from peat or biomass, in entrained flow, with an oxidizing medium containing free oxygen, comprising: a metering system for metering fuel through transport pipes; a high-capacity reactor connected to the transport pipes, said reactor having 3 gasification burners and an ignition and pilot burner at a head of the reactor; a system to measure and regulate amounts of pulverized fuel and oxygen flowing into the gasification burners with integral monitoring and regulation of overall total amounts of pulverized fuel and oxygen flowing to the reactor; a quenching chamber connected to the reactor for partial cooling of the crude gas and slag produced in the reactor; a waste heat boiler connected to the quenching chamber to recover steam with further cooling of crude gas and slag; and a water scrubber and partial condenser connected to the waste heat boiler.
 13. A device pursuant to claim 11, wherein each gasification burner has its own associated metering system.
 14. A device pursuant to claim 12, wherein each gasification burner has its own associated metering system. 